Solar generators or collectors are commonly used as power supplies for spacecraft such as telecommunication satellites. The terms "generator" and "collector" are used interchangeably herein. Solar collectors have panels that are initially folded for stowing the collector while transporting the satellite into an earth orbit. The panels are unfolded into an open state for deployment when the orbit has been reached. During the transport phase the collector shall need as little space as possible. On the other hand, the deployed surface area shall be as large as possible for transforming solar energy into electrical energy. Moreover, the deployment of the collector must be possibly free of trouble in order not to imperil the satellite's mission. Thus, a high degree of reliability particularly in the unfolding of the solar collector is necessary. Moreover, in order to test the kinematic and dynamic characteristics of the collector panels during an unfolding operation it must be possible to simulate such unfolding under gravity conditions on earth. Such testing must be possible with a minimum effort and expense.
Conventional solar generators of this type have a number of panels articulated to one another and foldable as well as unfoldable in a particular direction similar to the movement of the pleats of a bellows. The total deployed surface area of such solar collectors is limited by the acceptable maximal longitudinal extension of the panels away from the body of the satellite.
U.S. Pat. No. 4,988,060 (Janson et al.) discloses a solar collector with a plurality of panels interconnected to form panel wings which are symmetrically secured to a spacecraft. Hinges are arranged in alternate fashion along ridges of the individual panels sections so that the sections can be pulled out in the manner of pleats and folded back together into a package.
U.S. Pat. No. 4,293,731 (Schweig et al.) discloses a solar collector of lightweight construction including foldable panels. Journal pins passing through a journal loop and through a forked coupling provide hinges for the folding and unfolding.
European Patent Publication EP 0,754,625 A1 discloses a solar generator in which a first group of panels is foldable and unfoldable in one direction while further panels are foldable and unfoldable in a second direction. Such a structure increases the deployed surface area of the collector. The individual panels of the first group are connected by hinges and the panels of the second group are hinged to the first panel so that they can be flapped open. However, flapping open the panels of the second group causes relatively large disturbing moments that adversely affect the flight of the spacecraft. Another drawback is the fact that testing such generators with flap open motions under earth gravity conditions require a substantial effort and expense.
German Patent Publication DE 197 13 363 A1 discloses a method for increasing a surface area by first stacking surface elements that are partly interconnected by flap hinges and then unfolding the elements in the manner of a paper folding operation.
Aviation Week+Space Technology; Aug. 14, 1967, pages 72 to 88, describes in an article "Requirements for Solar Arrays Spurring New Techniques" various roll-up solar cell arrays.
Roll-up techniques can provide relatively large surface area panels when deployed. However, deployment can be problematic.
"Raumfahrtforschung" (Space Travel Research), Vol. 5, 1969, pages 205 to 212, describes in an article "New Technologic Methods for Solar Cell Devices" various requirements that must be met by solar collectors suitable for space travel. Advanced panel fabrication methods are disclosed that permit welding panel components and avoid using adhesives. Roll-out and fold-out collectors are described.